Rock drill bit



$- T. G. WILSHER ROCK DRILL BIT Oct. 11, 1949.

Filed Oct. 2'7, 1947 I N VEN TOR. Samue/ 760mm; Gem/(Mi/sef Patented Oct. 11, 1949 Samuel Thomas Erie, Pa.

Gerald Wilsher, Merritton, 0n-

tario, Canada, assignor to Charles E. Seley,

Application October 27, 1947, Serial No. 782,366

4 Claims.

This invention relates generally to drill bits and more particularly to detachable rock drill bits.

Present rockdrilling is performed by the utilization of percussive pneumatic rock drills which creates a rapid succession of impacts which are applied to long steel drill rods having the ends thereof forged and sharpened. Long steel drill rods have also been used with detachable drill bits wherein the bit delivers the drilling blows or impacts and penetrates the rock, pulverizing it and wearing out a round hole for disposing dynamite therein. Inasmuch as drilling operations are performed in most instances at a point quite remote from the shop where the drills are sharpened, detachable drill bits have been found desirable in that they are small and only three or four drill rods necessarily must be transported along with 50 or 60 small drill bits. Furthermore, the bits can be made from better steel. manufactured by better controlled processes, and be made into a better design for drilling. Detachable drill bits heretofore used have had straight radially extending cutting edges. These bits last about 2 minutes in moderately hard rock and it is necessary to remove and replace a bit with a new or sharpened bit. Present bits with radially extending cutting edges wear down on the outer portions thereof because the outer ends of the cutting edges must cut proportionately more rock than the inner edges and they therefore wear down two or three times as fast as the inner portion of the cutting blades.

It is, accordingly, an object of my invention to provide a novel rock drill bit which is simple in construction, economical in cost, efficient in oper- 'ation, and economical in manufacture.

Another object of my invention is to provide a rock drill bit which has two or more times the life of the rock drill bits now being used.

Another object of my invention is to provide a rock drill bit which will remain sharp over a comparatively long period of time.

Another object of my invention is to provide a rock drill bit having cutting blades which wear uniformly along their entire cutting surfaces.

Another object of my invention is to provide a rock drill bit having the cutting edges thereof of such contour that the cutting edges are autoat c y sharpened y e abrasive action of the rock while being drilled.

Another object of my invention is to provide a rock drill bit which gives more efficient sludge clearance and wherein the abrasive action of the rocl: particles will tend to sharpen the cutting tee h.

Another object of my invention is to provide a rock drill bit which will drill considerably faster than drill bits now being used.

Another object of my invention is to provide a rock drill bit which will drill a hole in a rock Wall free from jamming and one which sizes the hole better, thereby making less gage wear.

Other objects of my invention will become evident from the following detailed description, taken in conjunction with the accompanying drawings, in which Fig. 1 is an end view of my novel rock drill bit;

Fig. 2 is a side elevational view of my novel rock drill bit; and

Fig. 3 is a fragmentary view taken on the line 3--3 of Fig. 1 showing the contour of the cutting tooth.

Referring now to the drawings, Figs. 1 and 2 show acylindrically shaped drill bit I comprising a cylindrically shaped body portion 2 havin a central bore 3 and a counterbore 4. The counterbore 4 has the sides thereof tapered and provides a socket for receiving the spigot end of a drill rod (not shown). Extending radially outwardly and then curved in a predetermined arc, I form three equally spaced, arcuate shaped cutting teeth 6 on the face of the drill bit -I. The number of teeth b may be two, three, or more, without departing from the spirit of my invention.

The gist of my invention is the particular arcuate contour of the cutting teeth 6. The curvature of the teeth may vary within predetermined limits but I have found that the most efficient contour of the teeth 6 is one in which the curvature decreases and therefore the length of the cutting edge increases in proportion to the increase of the radius at any given point from the center of the drill bit. It Will be evident that the outside of the drill bit will travel through a much greater circumference than a point on the inside edge of a cutting tooth 6. It, therefore, requires a longer length of cutting tooth :to cut engaging surfaces on the outer side of the drill bit as rapidly as the engaging surfaces on the inner side of the drill bit. The cutting teeth 6 of the bit I will remain sharper on the outer sides of the teeth 6 by virtue of the curved profile and they will wear evenly along their entire length because of the uniformity of the cutting requirements at all points along the surface of the tooth.

As it will be noted in Fig. 3, the cutting teeth ii are triangular in cross-section with the upper cutting surface 1 thereof flat and it preferably should be approximately inch in width. The comparatively small fiat surface 1 on the cutting teeth assists in the drilling efiiciency in that there are no particularly sharp edges to wear oif immediately and the cutting surface will tend to sharpen themselves from the sludging and abrasive action of the rock passing between the teeth 6 in the lower contours 8 to the rear of the drill bit I.

In operation, my novel detachable drill bit is detachably secured to the end of a steel drilling rod and it is forced against a rock wall by means of a percussive pneumatic drill rotating the steel drill rod and applyin impacts on the rod and bit I. The bit cuts the rock uniformly along its entire cutting edge so that all parts of the cut ting edges of the teeth 6 wear uniformly.

It will be evident from the foregoing that I have provided a novel rock drill bit with cutting teeth which cuts the rocky uniformly along its entire cutting edge, which remains sharp longer, wears more uniformly, sharpens itself, one which drills more freely, one which sizes the hole better and saves gage wear, and one which lasts two or more times as long as present drill bits.

Various changes may be made in the specific embodiment of my invention without departing from the spirit thereof or from the scope of the appended claims.

What I claim is:

1. A drill bit comprising a body portion adapted to be connected to a rod, and laterally extending, arcuate shaped cutting teeth on one end of said body portion, the radius of curvature of said cutting teeth varying in proportion to the variation in radius outwardly from the center of said drill bit.

2. A drill bit as set forth in claim 1 wherein the engaging surfaces of said cutting teeth are flattened.

bit.

4. A rock drill bit as set forth in claim 3 wherein the engaging surfaces of said triangular shaped cutting teeth are flattened and are normal to the axis of said body portion of said drill bit.

SAMUEL THOMAS GERALD WILSHER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 895,387 Mercer Aug. 4, 1908 1,036,673 Meguire Aug. 27, 1912 1,318,958 Bernay Oct. i l, 1919 1,384,297 Bernay July 12, 1921 1,444,305 Christian Feb. 6, 1923 1,515,434 Gilman Nov. 11, 1924 1,698,873 Burke Jan. 15, 1929 2,022,194 Galvin Nov. 26, 1935 2,294,004 Serafino Aug. 25, 1942 FOREIGN PATENTS Number Country Date 24,652 Great Britain 1898 375,596 Great Britain June 30, 1932 455,098 France May 14, 1913 

